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931  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Lost values, again. on: August 17, 2009, 09:34:42 pm
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i don't think I saw any code running through the serial monitor at all when the 5v's where not connected.

I don't think connecting the supplies would have any big obvious effect, it's just bad practice..

I do think hooking up rx/tx between two arduinos won't work if one of them has pc serial running since it would be using the same pins.  
932  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Lost values, again. on: August 15, 2009, 12:24:51 pm
also, I don't think it's related but don't connect their 5V rails (unless one is powering the other).

could you describe exactly your wiring and computer hookup?  How do you know what you're sending and receiving?  Could the PC connection be interfering with the arduino-arduino link?

To simplify things, try sending steady spaces or 'A's or whatever to see what you get.
933  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Decoupling with polarized (tantalum) 0.1uF on: August 17, 2009, 09:25:42 pm
I was planning to use tantalum caps(.1 uf and 2.2 uf) on my L4931 power supply because they're physically smaller than the equivalent electrolytics - bad idea?
934  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: digital pins don't always work properly on: August 15, 2009, 08:39:40 pm
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I had a SPDT switch, 5v on the pole, ground on one side and pin 2 on the other.

So you could connect 5v to ground or 5v to pin 2?  I don't see either of those hurting the chip.  I would have a darned good look at the solder and traces around pins 6&7 (pins 12 & 13 on the AVR chip itself).

Putting your chip into a known good board should tell the tale.  They're not expensive if you need to replace it.
935  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: digital pins don't always work properly on: August 15, 2009, 04:05:42 pm
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The Specifications for the ATmega controller chip used on Arduino boards warn not to draw more than 40ma from a pin. They are not protected from over-current and you can damage the pins if you short them out.

The way I read it he had shorted +V, a pin, and ground.  It wouldn't seem the arduino could source much current with the +V shorted to ground.

I guess your point is though that it is possible to damage individual pins without borking the whole device.
936  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: digital pins don't always work properly on: August 15, 2009, 12:18:10 pm
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So I was wiring up a switch to enable the user to choose if he's plugging 4 or 8 lights and I probably shorted something. I had connected the +5v, digitalPin 2 and the ground to my switch but forgot to put a tie down resistor. So when I switched it, my computer gave me a warning that the usb port was drawing too much power.
As described that could draw too much power but i don't see it hurting the arduino.
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But now, the leds connected to digitalPin 11 and 12 are dimmed. It's not the leds as they work on other pins.
...I commented serialPrints and they started working properly. But now I'm having trouble with pins 6 and 7, yet 5 works. I'm not sure if they worked before as I had nothing connected before. I'm currently trying it out with the blink sketch (changing ledPin to 7, 6 and 5) so I'd be very surprised if it was a problem with the sketch. I also have nothing else connected or touchubg the board at the moment. Mind you, this time pin 6 and 7 are not dimmed, they just don't work at all.

Is there something special about pin 6 and 7 that I'm missing out on ? I don't mind connecting to say pin 5 and 4 but it seams I'm getting reliability issues here.
So this has moved around a lot.
What kind of board is it, did you buy it assembled or as a kit and which pins work/dont?

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After some pocking around with the multimeter, turns out when either pin 6 or 7 is on, both out .7v and when they are off they still output .2v, contrarily to the stable 0 of the other pins.
This sounds specifically like a hardware short of both pins to something but the whole business of pins 11 & 12 and the serial don't fit with that.
937  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: 12V & LED's on: July 30, 2009, 03:48:28 pm
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I connected 3 LED's in series to a 12V car battery. The LED's are rated 3.5V 4V max. The question is when the car is running the alternator is sending 14.5 so I was wondering about burning the LED's. Should I install a resistor in the circuit? What value should it be?

For sure you would need a resistor, you can figure out the value from the LEDs current consumption assuming you want to drop 4 volts across it - if the LED's want 40ma then you need like 100 ohms.

I would not be inclined to do this myself though.  I'm not sure how minor differences in the LEDs would affect the result.  There are "12 volt" LEDS meant for automotive use that don't need any coddling - could you try one of those instead?
938  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Serial Monitor VS Serial Output on: July 07, 2009, 03:52:58 pm
what IS the RS232 monitor and does it have any options?
939  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Serial Monitor VS Serial Output on: July 07, 2009, 12:06:05 pm
and is it expecting TTL levels vs RS232?
940  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Burning the bootloader with an Arduino? on: July 29, 2009, 10:34:21 am
don't get hung up on it. try one without the bootloaders and see if you run into any grief.  You still have a bunch of hills to climb to get your project going.
941  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Burning the bootloader with an Arduino? on: July 29, 2009, 09:50:36 am
the bootloader sits permanently at the top of the flash memory and can load new code over the serial port.  using an isp programmer like the one you posted or what i'm using does the same thing. so, yes, you can burn in a program and run it without the bootloader.

i think it's easier to use the arduino enviroinment with a loader though.
942  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Burning the bootloader with an Arduino? on: July 29, 2009, 09:06:18 am
i am using the code from http://code.google.com/p/mega-isp/  to burn sketches into attinys.  it's simple enough to use but i have not had occasion to use it with an atmega or bootloader.
943  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: PWM output on: July 30, 2009, 08:16:08 pm
it's also indicative that the smoothing is routinely needed.  I wouldn't mind seeing your code when it's ready to show.
944  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: PWM output on: July 30, 2009, 07:03:15 pm
you might want to dig into this thread which is about filtering accelerometer-type outputs. http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1248889032
945  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: PWM output on: July 28, 2009, 07:32:50 pm
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Is it a lilypad accelerometer with a LED on it attached to a lilypad processor?  If so it's not getting excess voltage and it should be perfectly happy.

Do you see the joggles on all three axes?  Do they happen when it's sitting still?  I would check the power and signal connections for starters.  If it's real data you'll have to filter it in software I guess.

I have a lilypad accelerometer here but it's not hooked up right now.  As I recall the data was pretty clean and I was not filtering it.  I did have code that reacted to large changes by moving only 25% toward the new value but I think that was mote to do with handling quick movements gracefully.
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